The creature I'm designing has a tail with spikes on the end of it. The material of the spikes should be strong/durable (not break easily), and very sharp (the edge as well as the sides, being able to cut through most materials like metal). The tail has several uses where these spikes might be a very real problem (like balancing, flexing around stuff to pick it up, and such). I'm looking for a way for the creature to protect itself and its surroundings from these spikes when they are not necessary.

So far I've come up with:

Retract them somehow (how? a long 'shard' is a bit different then a cat's claw for example, and they should not cut themselves when retracting them)

Vice versa: cover them with skin or something similar (how?)

Make them less 'spiky' or only sharp at the very edge (but then they become less useful in my world)

Just naturally learn to live with it (but that seems like a cheap way out)

I guess there is a reason most animals have either retractable claws or no claws if they need their hands/feet. But would there be a solution that is (biologically speaking) logical / plausible?

I couldn't find a question that addresses something like this. Retractable claws have been discussed:
Retractable claws in otherwise human-like hands?
But these are (curved) claws on fingers; I'm not sure if their design would work on my creature ('shards' on a tail).

$\begingroup$Diamond is hard but it not strong and easily fractures, it's not a good material for an claw or spike. You need to understand what properties you want your spike to have.$\endgroup$
– SarriesfanJan 20 '18 at 11:21

$\begingroup$I pity the mother who gave birth to this creature.$\endgroup$
– Justin ThymeJan 20 '18 at 15:40

1

$\begingroup$I'm not sure exactly what form you plan on having these creatures take, but I might point you toward looking at how modern animals deal with these types of issues. In addition, there have been many extinct animals (stegosaurs, ankylosaurs, and glyptodonts all come to mind) that utilized spiky weapons on or around their tails, so that might be worth looking into.$\endgroup$
– TheTimeVoyagerJan 20 '18 at 18:15

4 Answers
4

Have you considered folding spikes? Rather than trying to retract them into the body, perhaps instead the spikes fold back against the tail when they're not needed.

Properly designed, the spikes can be made much safer folded back than fanned out. Imagine a razor - if you press your finger against the blade it will cut you, but if you stack five together so their blades are flat with each other they barely cut at all. Perhaps your creatures' tails fold back like that.

Such powerful spikes also need maintenance- you can't just drop them and regrow like a porcupine. Culturally your creatures might let their tails blunt and only sharpen them for war (an adaptation to denser society). They may also wear clothing over the top to protect their spikes and others.

More generally, consider why your creatures evolved such fantastic weapons - there may be arrangements of spikes (eg. forming a blade facing out) that provide utility for its ancient use cases without exposing yourself to too much self-harm.

$\begingroup$This has possibilities. Think scales, with sharp edges. Normally, they lie flat, overlapping each other. But through contraction and extension of muscles, they could open up like a pine cone.$\endgroup$
– Justin ThymeJan 20 '18 at 15:44

$\begingroup$I had not thought of folding yet. This and the other answer together will help me in my world :)$\endgroup$
– CenturyJan 25 '18 at 20:05

How do humans go through life not poking themselves in the eye with a finger? How to Rhinos not gore every rhino they meet? How does a rolling horse not roll over its colt? How did my pet iguana not slap itself into a stupor when it let that very leathal tail off its leash?

The tail may have a physiological limitation that prohibits it from swinging all the way into the creature itself. This exists on iguanas, they literally cannot swing their tail far enough to hurt themselves. (Note: the physics of a spiked tail might not allow it even if it could. It has weight, and that weight must be accomodated when swung. The creature's body may be forced by leverage to swing out of the way when the tail is swung to that extent. It's just another expression of this limitation.)

All creatures learn to live within the limitations of their existence. I've seen my cat wrap its tail into its ear to sleep, but you never see it tripping over its own tail when it walks or runs. The same is true with human arms. We learn not to poke our eyes. I'm sure that dinosaurs with spiky tails were not born with the spikes and as the spikes grew, the dinos learned not to hit themselves with the spikes.

All creatures that can see learn to see where other things are. This is the least perfect of the issues I'm presenting, but we learn to see the world around us and we learn to know our place in it. This is why people throwing bolas, lassos and jumping ropes don't hit themselves or tangle themselves with the items, they have a sense of where they are in relation to what they're doing.

So, realistically, the "cheap way out" is how nature actually solved the problem.

But, if you're looking for something with greater literary coolness... remember that cats retract their claws. This has more to do with protecting the claw than it does protecting the cat (the claws come out when they scratch an itch), but it's a solution.

Limit the range of motion of the tail, accounting for momentum and any free movement the spikes may have, so it is physically unable to double back and strike the body of the animal. The easiest way to do this would likely be to elongate the tail vertebrae, strengthen the tendons that connect them, and thicken the overall musculature.

Some scientists think that dinosaurs had many types of skin (some had skin, other feathers or scales). You could "give" your creature a hard skin or scales to protect herself from her spikes. Also you could give her some hardened plates that could be placed in a way that the spikes should hit them instead of the flesh of the creature.

I don't think many creatures can "hurt themselves" with their own defense system.

$\begingroup$Welcome to WorldBuilding Lucas! Interesting answer. If you have a moment please take the tour and visit the help center to learn more about the site. Have fun!$\endgroup$
– SecespitusJan 22 '18 at 12:07